The gene editing revolution began as soon as CRISPR, a sequence of DNA discovered in some microorganisms that can splice our genetic code, was discovered. So far it's been used to modify the DNA of agricultural plants and animals, mosquitoes, lab animals, and many other living things. One thing it hadn't been used to modify, however, was a human embryo — and for good reason. Tinkering with the human genetic code is considered a major ethical no-no.

Unfortunately, that didn't stop one Chinese scientist, He Jiankui of the Southern University of Science and Technology, from doing it anyway.

Last year, He and his team used CRISPR to modify the genes of twin girls, called Lulu and Nana, and when the experiment went public, it caused outcry around the world. The Chinese team insisted that the only modification they made was to delete a gene called CCR5, in an attempt to make the children resistant to HIV infection. Humans born naturally without CCR5 are known to be immune to HIV.

But now it turns out that HIV may only have been the experiment's secondary concern. There are reports that Lulu and Nana were also purposely given brain enhancements, reports MIT Technology Review.

“The answer is likely yes, it did affect their brains,” said Alcino J. Silva, a neurobiologist at the University of California, Los Angeles.

Silva's lab at UCLA recently uncovered another key role of the CCR5 gene in our brains. Apparently, CCR5 acts as a neural suppressant that can affect your memory and your brain's ability to make new connections. When CCR5 is deleted in lab mice, their memory and cognitive function gets a measurable boost.

This is information that He and the Chinese team would have had access to prior to performing their modifications on Lulu and Nana. And ethical watchdogs around the world are now looking at whether making brain enhancements was He's original intent.

Either way, the damage is done. While cognitive enhancements might sound like a good thing to some, it's important to keep in mind that such modifications can lead down a slippery slope; a future where the human population is segregated between those who have been given enhancements and those who might be considered inferior. There are also fears that once super-intelligent humans are created, it could lead to a biotechnology race between nations that would forever alter our species in unpredictable ways.

Furthermore, we already have CCR5-related methods for treating HIV that don't require modification of anyone's genetic code. For instance, there is an anti-HIV drug, Maraviroc, which chemically blocks CCR5.

There are also studies being performed on whether those taking Maraviroc experience cognitive enhancements. Those findings could open up a whole other ethical can of worms, but it's an arena that's more navigable than attempting to run the gauntlet of genetic modification.

“Cognitive problems are one of the biggest unmet needs in medicine. We need drugs, but it’s another thing to take normal people and muck with the DNA or chemistry to improve them,” said Silva. “We simply don’t know enough to do it. Nature has struck a very fine balance.”

China's genetically engineered twins were secretly given brain enhancements
A controversial CRISPR experiment on humans just got even more heated.